This invention relates to methods and pharmaceutical compositions for specifically modifying an immune response to an antigen. The methods include treating an antigen presenting cell to enhance expression of the major histocompatibility complex molecules, followed by reacting the treated antigen presenting cells with an antigen extracorporeally to form an antigen-associated antigen presenting cell.
Immune system responses may be classified as humoral or cell-mediated. A humoral response is mediated by B lymphocytes in the form of freely diffusible antibody molecules. A cell-mediated response is mediated by specifically-reactive lymphocytes, such as T lymphocytes (xe2x80x9cT cellsxe2x80x9d), rather than antibodies.
T cells react with foreign antigens via surface receptors that are distinctive for each T cell clone. The T cell surface receptors are generally composed of two disulfide-linked protein chains having unique amino acid sequences (Edelson, R., xe2x80x9cPhotopheresis: A Clinically Relevant Immunobiologic Response Modifierxe2x80x9d, Annals of N.Y. Academy of Sciences 636:154-164 (1991). The physical properties of these receptors confer specific binding capabilities and permit each of the several million clones of T cells in an individual to operate independently.
The T cell receptor is capable of recognizing a particular antigen only when it is associated with a surface marker on an antigen presenting cell, such as a macrophage. The surface markers belong to a group of molecules known as the major histocompatibility complex (MHC). Binding of the T cell receptor to the antigen on the antigen presenting cell induces changes in the T cell, which changes collectively comprise the cell-mediated response.
The induction of expression of xe2x80x9cemptyxe2x80x9d, i.e., devoid of peptide, major histocompatibility complex class I molecules under conditions of reduced temperature has been demonstrated in a murine lymphoma mutant cell line (Ljunggren et al., Nature 346:476-480 (1990)). The mutant cell line lacks the appropriate intracellular mechanism for loading intracellular peptides into the binding clefts of newly synthesized class I molecules. The mutant cell line class I molecules are substantially empty and thermodynamically unstable at 37xc2x0 C., but are stabilized by providing an exogenous source of peptides which bind to the empty class I molecules. An increased level of major histocompatibility complex class I expression has also been reported for a corresponding wild-type cell line (ibid.) when grown at temperatures below 37xc2x0 C. However, the tests used to identify class I expression in that system did not distinguish between empty class I and class I molecules associated with peptide.
Improvement in the relatively inefficient exchanging of an exogenously added peptide for peptides already present in the clefts of class I molecules by the addition of exogenous free beta-2-microglobulin has also been demonstrated (Rock et al., PNAS (USA) 87:7517-7521 (1990).
Two signals are primarily responsible for inducing the T cell mediated response to an antigen presenting cell which is associated with antigen. A first signal is due to binding of the T cell to the antigen on the antigen presenting cell. A second, co-stimulatory signal is sent by xe2x80x9caccessoryxe2x80x9d membrane molecules or soluble messengers from the antigen presenting cell to the responding T cell. These soluble intercellular messengers regulate the amplitude and duration of the immune response and are given the generic term, cytokines. Cytokines include the group previously referred to as lymphokines, monokines, interleukins and interferons (Essential Immunology, seventh edition, Blackwell Scientific Publications, Oxford, Great Britain, 1991, pp. 140-150). If the antigen presenting cell does not send the second signal, the T cell is effectively paralyzed, i.e., unable to mount an immune response to the antigen. Certain types of antigen presenting cells, e.g., resting T cells, are unable to send the second signal. Accordingly, in the absence of exogenous cytokine or other second signal, such resting T cells which function as antigen presenting cells down-regulate an immune response to the presented antigen and lead to antigen specific immunologic paralysis of the T cell whose membrane receptor has been engaged.
T cells also function in regulation of an immune response via recognition by the immune system of the T cell surface receptor. Thus, several studies, described herein, have suggested that the ability of the immune system to recognize the receptor of an aberrant T cell clone as antigenic makes possible the vaccination of a patient against a pathogenic clone of T cells.
Cutaneous T cell lymphoma (CTCL) is an example of an immune system disease that is caused by a massive expansion of a single clone of aberrant T cells. Extracorporeal photochemotherapy (xe2x80x9cphotopheresisxe2x80x9d) for the treatment of cutaneous T cell lymphoma has been described (Edelson, R., xe2x80x9cLight-activated Drugsxe2x80x9d, Scientific American 256(8): 68-75 (1988); Edelson, R., xe2x80x9cPhotopheresis: A Clinically Relevant Immunobiologic Response Modifierxe2x80x9d, Annals of N.Y. Academy of Sciences 636:154-164 (1991). The treatment comprises isolating the patient""s T cells, irradiating the cells in the presence of a photoactivatable agent (8-MOP) and reinfusing the damaged T cells. The 8-MOP is activated by the ultraviolet light to form a transient molecule capable of photomodifying cellular DNA. This therapy reportedly results in selective destruction of the malignant T cell clone.
It is believed that exposure of the malignant clone to 8-MOP and ultraviolet light, followed by return of the irradiated, damaged cells to the patient, elicits a specific response to the aberrant T cells that is mediated by T cell surface receptors, i.e., the damaged cells of the malignant clone had, in effect, primed the immune system to specifically destroy the clone. In essence, photopheresis xe2x80x9cvaccinatedxe2x80x9d the CTCL patients against their own cancer.
Photopheresis has also been used for the treatment of several autoimmune disorders, including pemphigus vulgaris and systemic sclerosis (Rook, A., xe2x80x9cPhotopheresis in the Treatment of Autoimmune Disease: Experience with Pemphigus Vulgaris and Systemic Sclerosisxe2x80x9d, Annals of N.Y. Academy of Science 636:209-216 (1991) and rheumatoid arthritis (Malawista, S., et al., xe2x80x9cPhotopheresis for Rheumatoid Arthritisxe2x80x9d, Annals of N.Y. Academy of Science 636:217-226 (1991).
U.S. Pat. No. 4,838,852, issued to Edelson et al. (hereinafter Edelson ""852), the contents of which are incorporated herein by reference, describes a method for altering the immune system response of a mammal to an antigen. The Edelson ""852 method comprises (a) contacting the subject""s immune system with the specific antigen for a suitable time to artificially stimulate the immune system, (b) withdrawing antigen-stimulated blood cell material from the subject, (c) treating the withdrawn material to alter the antigen-stimulated cells, and (d) returning the treated material to the subject. Contacting the subject""s immune system with the specific antigen is achieved in any manner which introduces the antigen into the mammal""s immune system, e.g., by injecting directly into the blood stream, the lymphatic system or the lymphoid organs. Edelson ""852 also discloses that it may be possible to render the cells incapable of recognizing an antigen by withdrawing the blood cell containing material from the subject, treating the withdrawn material as above, returning the treated material to the subject and then contacting the subject""s immune system with a specific antigen.
U.S. Pat. No. 5,147,289, issued to Edelson (hereinafter Edelson ""289), the contents of which are incorporated herein by reference, describes methods for non-specifically enhancing the immune system response of a mammal to an antigen. The method comprises (A) enhancing the immune system response by (a) withdrawing leukocyte containing material from the mammal, (b) treating the withdrawn leukocytes in a manner to alter the cells, (c) returning the treated leukocytes to the mammal and (B) artificially contacting the mammal""s immune system with the antigen for a suitable period of time to stimulate an immune system response.
With respect to the Edelson ""852 and ""289 patents, the withdrawn leukocytes may be altered by, for example, inactivating the cells by photopheresis, exposing the cells to high or low temperature, high or low pH values, high or low pressure, hypotonic solutions, chemotherapeutic agents, or a variety of other inactivating conditions.
Photopheresis also has been used prophylactically to prevent graft rejection by injecting into mice a preparation containing Photoinactivated Effector T (xe2x80x9cPETxe2x80x9d) cells (Perez, M. et al., xe2x80x9cInhibition of Antiskin Allograft Immunity Induced by Infusions with Photoinactivated Effector T Lymphocytes (PET Cells); xe2x80x9cThe Congenic Modelxe2x80x9d, Transplantation 51:1283-1289 (1991). To prepare the PET cells, T cell clones mediating skin graft rejection were expanded in vivo and photoinactivated using 8-MOP. Perez et al. report that this procedure results in the adoptive transfer of tolerance for skin allotransplantation, as demonstrated by prolongation of allograft survival in the recipients of PET cells.
A preliminary study to evaluate the potential therapeutic value of photopheresis in seven patients with AIDS-related complex (ARC) has been reported (Bisaccia, E. et al., xe2x80x9cViral-Specific Immunization in AIDS-Related Complex by Photopheresisxe2x80x9d, Annals of N.Y. Academy of Science 636:321-330 (1991). One advantage of photopheresis for the treatment of an immunocompromised patient, such as an AIDS patient, is that unlike antiviral drug treatments, extracorporeal photopheresis spares the tissue-fixed elements of the immune system from exposure to the therapy, thereby minimizing damage to the antigen processing system.
Photopheresis has been demonstrated to produce a generalized clinical benefit for a variety of autoimmune diseases that are characterized by a disorder in T cell regulation. In addition to producing an immunization effect against clones of autoreactive T cells, photopheresis may also result in induction of soluble extracellular messengers, e.g., tumor necrosis factor, which have a therapeutic adjuvant effect for a number of disease states.
The above-described therapies have in common the ability to vaccinate against a particular T cell activity without isolating or identifying the clone(s) responsible for the activity. None of the cited references and/or patents disclose a method for specifically regulating an immune system response. Accordingly, there is still a need for methods and pharmaceutical compositions to precisely regulate the immune system response to a specific antigen. Such methods would permit stimulation of a competent or incompetent immune system and would permit the stimulation of an immune system in a subject already weakly stimulated with the antigen. Preferably, such methods and compositions would permit stimulation of the immune system in the form of booster immunizations.
The present invention provides methods and pharmaceutical compositions for specifically modifying an immune system response to an antigen. In particular, the invention provides methods and compositions for actively immunizing patients against malignant cells or lymphocytes responsible for autoimmune disease. Also provided are methods for inducing immunologic tolerance to autologous or exogenous antigens and compositions useful in suppressing clinically undesirable immunologic reactions.
According to one aspect of the invention, a method for forming an antigen-associated antigen presenting cell is provided. The method comprises treating a preparation containing an antigen presenting cell to enhance expression by the cell of a major histocompatibility complex molecule and reacting the treated antigen presenting cell with the antigen extracorporeally to form an antigen-associated antigen presenting cell. In a preferred embodiment, the antigen presenting cells are T cells which have been treated to enhance expression of the major histocompatibility complex class I molecules and the antigens are peptides. The peptide antigens are associated with a solid tumor malignancy, an immunodeficiency disease or a hypersensitivity disease.
A preferred method for enhancing expression of the major histocompatibility complex molecules is by subjecting the preparation containing the antigen presenting cells to room temperature. Alternate methods of treatment of the antigen presenting cells also are provided.
According to another aspect of the invention, a method for making a pharmaceutical preparation for administration to a mammal is provided. The method comprises placing the above-described antigen-associated antigen presenting cell, or components of same, in a pharmaceutically acceptable carrier.
According to yet another aspect of the invention, a method for specifically modifying the immune system response of a mammal to an antigen is provided. The method comprises administering the above-described pharmaceutical preparation to the mammal. In a preferred embodiment, the antigen presenting cells are isolated from a human recipient, treated and returned to the patient Pin the form of antigen-associated antigen presenting cells. Optionally, the pharmaceutical preparation is stored in aliquots containing an amount of antigen-associated antigen presenting cells sufficient to boost the immune response of the patient. Selection of an amount of cells necessary to boost the patient""s immune response is within the capabilities of those skilled in the art without the need for undue experimentation. The amount of cells is, in part, dependent upon the patient""s age, weight and medical profile. Preferably, an amount of cells ranging from a minimum of about 25,000 to a maximum of about 200xc3x97106 antigen presenting cells is sufficient to boost the immune response of the patient (Ben-Nun, A., et al., xe2x80x9cVaccination against autoimmune encephalomyelitis with T lymphocyte line cells reactive against myelin basic proteinxe2x80x9d, Nature 292:60-61 (1981); Holoshitz, J., et al., xe2x80x9cLines of T lymphocytes induce or vaccinate against autoimmune arthritisxe2x80x9d, Science 219:56-58 (1983); Lider, O., et al., xe2x80x9cAnti-idiotypic network induced by T cell vaccination against experimental autoimmune encephalomyelitisxe2x80x9d, Science 239:181-183 (1988); Khavari, P., et al., xe2x80x9cSpecific vaccination against photoinactivated cloned T cellsxe2x80x9d, Abstract Clin. Res. 36:662A (1988); and Edelson, R., et al. xe2x80x9cTreatment of cutaneous T cell lymphoma by extracorporeal photochemotherapyxe2x80x9d, N. Engl. J. Med. 316:297-303 (1987).
In one embodiment, treatment of the antigen presenting cells to enhance expression of the major histocompatibility complex molecules comprises irradiating the antigen presenting cells in the presence of a photoactivatable agent. In some instances, the photoactivatable agent may be administered orally to the patient prior to the enhancement step.
According to still another aspect of the invention, a pharmaceutical composition for modifying an immune system response to an antigen is provided. The composition comprises a pharmaceutically acceptable carrier and a plurality of antigen presenting cells, each cell having on its surface a major histocompatibility complex molecule associated with an antigen. In a preferred embodiment, the plurality of major histocompatibility complex molecules represent a relatively homogeneous population. The antigen presenting cells of the present invention have an elevated concentration of major histocompatibility molecules compared to corresponding, naturally occurring antigen presenting cells. The preparation contains an amount of antigen presenting cells sufficient to modify the patient""s immune system response. Selection of an amount of cells necessary to modify the patient""s immune response is within the capabilities of those skilled in the art without the need for undue experimentation. The amount of cells is, in part, dependent upon the patient""s age, weight and medical profile. Preferably, an amount of cells ranging from a minimum of about 25,000 to a maximum of about 200xc3x97106 antigen presenting cells is sufficient to boost the immune response of the patient. (Ben-Nun, A., et al., supra.; Holoshitz, J., et al., supra.; Lider, O., et al., supra.; Khavari, P., et al., supra.; and Edelson, R., et al., N. Engl. J. Med. 316, supra.
These and other aspects of the invention as well as various advantages and utilities will be more apparent with reference to the detailed description of the preferred embodiments and in the accompanying drawings.